Glennan estimated that 5 percent of Northrop Grumman's employees use Firefox. He said that if the usage level creeps up to 10 percent, he might consider having the IT department support the browser.

In the meantime, Glennan is weighing the prospects of adding Firefox as an alternative standard in the event of a catastrophic problem with IE, or as an option for users who need to test code against Firefox. But there is no large-scale plan to push out multiple browsers on an enterprisewide basis.

Randy Kortering, global information systems integration director at Haworth Inc. in Holland, Mich., said the office furniture maker considered Firefox because "Microsoft has a bull's-eye on it for malware writers," whereas the less widely deployed open-source browser gives them fewer potential victims. But in the end, Haworth's reliance on applications that use functionality in IE stopped it from moving past the consideration stage, he said.

Ron Cook, CTO at RadioShack Corp. in Fort Worth, Texas, faces the same dilemma. Some of the retail chain's older internal Web sites rely on ActiveX controls that run only with Microsoft's browser. Using Firefox would require users to log on multiple times, Cook said.

Software updates are another issue. RadioShack uses Microsoft's Windows Update services, and if it switched to Firefox, IT would have to come up with a different update mechanism, Cook noted.